Stable iminonitroxide biradical in the triplet ground state

Chemistry Letters

Volumn 33, Issue 11, 2004, Pages 1494-1495

  Hayakawa, Kenichi ^a   Shiomi, Daisuke ^a,b   Ise, Tomoaki ^a,b   Sato, Kazunobu ^a   Takui, Takeji ^a  

^a Osaka Prefecture University   (Japan)

^b JAPAN SCIENCE AND TECHNOLOGY AGENCY   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

NITROXIDE; PYRIDINE DERIVATIVE; RADICAL;

ARTICLE; CHEMICAL BOND; COVALENT BOND; MAGNETISM; REACTION ANALYSIS; STRUCTURE ANALYSIS;

EID: 13544271923     PISSN: 03667022     EISSN: None     Source Type: Journal    
DOI: 10.1246/cl.2004.1494     Document Type: Article

References (33)

1. For recent overviews of molecule-based magnetism, see: "Magnetic Properties of Organic Materials," ed. by P. M. Lahti, Marcel Dekker, New York (1999); "Molecular Magnetism," ed. by K. Itoh and M. Kinoshita, Gordon and Breach, Amsterdam, Kodansha, Tokyo (2000).
2. For recent overviews of molecule-based magnetism, see: "Magnetic Properties of Organic Materials," ed. by P. M. Lahti, Marcel Dekker, New York (1999); "Molecular Magnetism," ed. by K. Itoh and M. Kinoshita, Gordon and Breach, Amsterdam, Kodansha, Tokyo (2000).
3. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
4. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
5. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
6. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
7. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
8. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
9. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
10. Molecular pairing based on hydrogen bonding or ionic charges has been reported for S = 1/2 radicals: J. Cirujeda, L. E. Ochando, J. M. Amigo, C. Rovira, J. Rius, and J. Veciana, Angew. Chem., Int. Ed. Engl., 34, 55 (1995); J. Cirujeda, M. Mas, E. Molins, F. Lanfranc de Panthou, J. Laugien, J. G. Park, C. Paulsen, P. Rey, C. Rovira, and J. Veciana, J. Chem. Soc., Chem. Commun., 1995, 709; J. Veciana, J. Cirujeda, C. Rovira, E. Molins, and J. J. Novoa, J. Phys. I, 6, 1967 (1996); M. M. Matsushita, A. Izuoka, T. Sugawara, T. Kobayashi, N. Wada, N. Takeda, and M. Ishikawa, J. Am. Chem. Soc., 119, 4369 (1997); H. Nagashima, N. Yoshioka, and H. Inoue, Polyhedron, 20, 1151 (2001); T. Otsuka, T. Okuno, K. Awaga, and T. Inabe, J. Mater. Chem., 8, 1157 (1998); K. Awaga, A. Yamaguchi, T. Okuno, T. Inabe, T. Nakamura, M. Matsumoto, and Y. Maruyama, J. Mater. Chem., 4, 1377 (1994); P. M. Lahti, J. R. Ferrer, C. George, P. Oliete, M. Julier, and F. Palacio, Polyhedron, 20, 1465 (2001).
11. The crystal engineering approach to molecule-base ferrimagnets with charged open-shell molecules has been reported: D. Shiomi, K. Ito, M. Nishizawa, K. Sato, T. Takui, and K. Itoh, Synth. Met., 103, 2171 (1999); K. Kamiyama, D. Shiomi, S. Hase, M. Nishizawa, K. Sato, M. Kozaki, K. Okada, and T. Takui, Appl. Magn. Reson., 19, 45 (2000); D. Shiomi, M. Nishizawa, K. Kamiyama, S. Hase, T. Kanaya, K. Sato, and T. Takui, Synth. Met., 121, 1810 (2001); S. Hase, D. Shiomi, K. Sato, and T. Takui, J. Mater. Chem., 11, 756 (2001); S. Hase, D. hiomi, K. Sato, and T. Takui, Polyhedron, 20, 1403 (2001).
12. The crystal engineering approach to molecule-base ferrimagnets with charged open-shell molecules has been reported: D. Shiomi, K. Ito, M. Nishizawa, K. Sato, T. Takui, and K. Itoh, Synth. Met., 103, 2171 (1999); K. Kamiyama, D. Shiomi, S. Hase, M. Nishizawa, K. Sato, M. Kozaki, K. Okada, and T. Takui, Appl. Magn. Reson., 19, 45 (2000); D. Shiomi, M. Nishizawa, K. Kamiyama, S. Hase, T. Kanaya, K. Sato, and T. Takui, Synth. Met., 121, 1810 (2001); S. Hase, D. Shiomi, K. Sato, and T. Takui, J. Mater. Chem., 11, 756 (2001); S. Hase, D. hiomi, K. Sato, and T. Takui, Polyhedron, 20, 1403 (2001).
13. The crystal engineering approach to molecule-base ferrimagnets with charged open-shell molecules has been reported: D. Shiomi, K. Ito, M. Nishizawa, K. Sato, T. Takui, and K. Itoh, Synth. Met., 103, 2171 (1999); K. Kamiyama, D. Shiomi, S. Hase, M. Nishizawa, K. Sato, M. Kozaki, K. Okada, and T. Takui, Appl. Magn. Reson., 19, 45 (2000); D. Shiomi, M. Nishizawa, K. Kamiyama, S. Hase, T. Kanaya, K. Sato, and T. Takui, Synth. Met., 121, 1810 (2001); S. Hase, D. Shiomi, K. Sato, and T. Takui, J. Mater. Chem., 11, 756 (2001); S. Hase, D. hiomi, K. Sato, and T. Takui, Polyhedron, 20, 1403 (2001).
14. The crystal engineering approach to molecule-base ferrimagnets with charged open-shell molecules has been reported: D. Shiomi, K. Ito, M. Nishizawa, K. Sato, T. Takui, and K. Itoh, Synth. Met., 103, 2171 (1999); K. Kamiyama, D. Shiomi, S. Hase, M. Nishizawa, K. Sato, M. Kozaki, K. Okada, and T. Takui, Appl. Magn. Reson., 19, 45 (2000); D. Shiomi, M. Nishizawa, K. Kamiyama, S. Hase, T. Kanaya, K. Sato, and T. Takui, Synth. Met., 121, 1810 (2001); S. Hase, D. Shiomi, K. Sato, and T. Takui, J. Mater. Chem., 11, 756 (2001); S. Hase, D. hiomi, K. Sato, and T. Takui, Polyhedron, 20, 1403 (2001).
15. The crystal engineering approach to molecule-base ferrimagnets with charged open-shell molecules has been reported: D. Shiomi, K. Ito, M. Nishizawa, K. Sato, T. Takui, and K. Itoh, Synth. Met., 103, 2171 (1999); K. Kamiyama, D. Shiomi, S. Hase, M. Nishizawa, K. Sato, M. Kozaki, K. Okada, and T. Takui, Appl. Magn. Reson., 19, 45 (2000); D. Shiomi, M. Nishizawa, K. Kamiyama, S. Hase, T. Kanaya, K. Sato, and T. Takui, Synth. Met., 121, 1810 (2001); S. Hase, D. Shiomi, K. Sato, and T. Takui, J. Mater. Chem., 11, 756 (2001); S. Hase, D. hiomi, K. Sato, and T. Takui, Polyhedron, 20, 1403 (2001).
16. G. Ulrich and R. Ziessel, Tetrahedron Lett., 35, 1215 (1994); G. Ulrich and R. Ziessel, Tetrahedron Lett., 35, 1211 (1994).
17. G. Ulrich and R. Ziessel, Tetrahedron Lett., 35, 1215 (1994); G. Ulrich and R. Ziessel, Tetrahedron Lett., 35, 1211 (1994).
18. H. Oshio, T. Watanabe, A. Ohto, and T. Ito, Inorg. Chem., 36, 1608 (1997); H. Oshio, M. Yamamoto, and T. Ito, J. Chem. Soc., Dalton Trans., 1999, 2641; H. Oshio, M. Yamamoto, T. Ito, H. Kawauchi, N. Koga, T. Ikoma, and S. Tero-Kubota, Inorg. Chem., 40, 5518 (2001); H. Oshio, M. Yamamoto, H. Kawauchi, N. Koga, and T. Ito, J. Solid State Chem., 159, 455 (2001).
19. H. Oshio, T. Watanabe, A. Ohto, and T. Ito, Inorg. Chem., 36, 1608 (1997); H. Oshio, M. Yamamoto, and T. Ito, J. Chem. Soc., Dalton Trans., 1999, 2641; H. Oshio, M. Yamamoto, T. Ito, H. Kawauchi, N. Koga, T. Ikoma, and S. Tero-Kubota, Inorg. Chem., 40, 5518 (2001); H. Oshio, M. Yamamoto, H. Kawauchi, N. Koga, and T. Ito, J. Solid State Chem., 159, 455 (2001).
20. H. Oshio, T. Watanabe, A. Ohto, and T. Ito, Inorg. Chem., 36, 1608 (1997); H. Oshio, M. Yamamoto, and T. Ito, J. Chem. Soc., Dalton Trans., 1999, 2641; H. Oshio, M. Yamamoto, T. Ito, H. Kawauchi, N. Koga, T. Ikoma, and S. Tero-Kubota, Inorg. Chem., 40, 5518 (2001); H. Oshio, M. Yamamoto, H. Kawauchi, N. Koga, and T. Ito, J. Solid State Chem., 159, 455 (2001).
21. H. Oshio, T. Watanabe, A. Ohto, and T. Ito, Inorg. Chem., 36, 1608 (1997); H. Oshio, M. Yamamoto, and T. Ito, J. Chem. Soc., Dalton Trans., 1999, 2641; H. Oshio, M. Yamamoto, T. Ito, H. Kawauchi, N. Koga, T. Ikoma, and S. Tero-Kubota, Inorg. Chem., 40, 5518 (2001); H. Oshio, M. Yamamoto, H. Kawauchi, N. Koga, and T. Ito, J. Solid State Chem., 159, 455 (2001).
22. w = 0.2030 (GOF = 1.001) for 2537 unique reflections (I > 2σ(I)) and 250 parameters. The large R value results from the disorder as described in the text. The occupancies of the disordered carbon atoms are optimized in two conformations: C9/C20 = 0.68/0.32, C10/C21 = 0.59/0.41, C11/C22 = 0.68/0.32, C12/C23 = 0.66/0.34.
23. The spin density distribution of 1 in the triplet state was calculated with the unrestricted density functional theory at the UB3LYP/6-31+G(d,p) level using a program package Gaussian 98. The molecular geometry was taken from the X-ray crystal structure. M. J. Frisch, et al, "Gaussian 98, Revision A.9," Gaussian, Inc., Pittsburgh PA (1998).
24. 2 solution of PVC and 1 was slowly evaporated to give a film, which was used in the susceptibility measurement. The reduced purity of 0.966 is attributed to decomposition during the slow evaporation.
25. B. D. Bleany and K. Bowers, Proc. R. Soc. London, Ser. A, 214, 451 (1952).
26. B = 0.22 mT, the g-factor of g = 2.0065, and the linewidth of 0.12 mT for the Lorentzian lines.
27. M. E. Fisher, Am. J. Physiol., 32, 343 (1964).
28. FM was, however, kept unchanged in the simulation with Eq 2 in order to avoid overparameterization.
29. L. Catala, J. Le Moigne, N. Kyritsakas, P. Ray, J. J. Novoa, and P. Turek, Chem. - Eur. J., 7, 2466 (2001); H. Oshio, A. Ohto, J. Fujisawa, T. Watanabe, T. Ito, and K. Isobe, Chem. Lett., 1994, 2353; T. Sugano, M. Tamura, and M. Kinoshita, Synth. Met., 56, 3305 (1993); D. Shiomi, K. Ito, M. Nishizawa, A. Hase, K. Sato, T. Takui, and K. Itoh, Mol. Cryst. Liq. Cryst., 334, 99 (1999); D. Shiomi, M. Tamura, H. Sawa, R. Kato, and M. Kinoshita, j. Phys. Soc. Jpn., 62, 289 (1993).
30. L. Catala, J. Le Moigne, N. Kyritsakas, P. Ray, J. J. Novoa, and P. Turek, Chem. - Eur. J., 7, 2466 (2001); H. Oshio, A. Ohto, J. Fujisawa, T. Watanabe, T. Ito, and K. Isobe, Chem. Lett., 1994, 2353; T. Sugano, M. Tamura, and M. Kinoshita, Synth. Met., 56, 3305 (1993); D. Shiomi, K. Ito, M. Nishizawa, A. Hase, K. Sato, T. Takui, and K. Itoh, Mol. Cryst. Liq. Cryst., 334, 99 (1999); D. Shiomi, M. Tamura, H. Sawa, R. Kato, and M. Kinoshita, j. Phys. Soc. Jpn., 62, 289 (1993).
31. L. Catala, J. Le Moigne, N. Kyritsakas, P. Ray, J. J. Novoa, and P. Turek, Chem. - Eur. J., 7, 2466 (2001); H. Oshio, A. Ohto, J. Fujisawa, T. Watanabe, T. Ito, and K. Isobe, Chem. Lett., 1994, 2353; T. Sugano, M. Tamura, and M. Kinoshita, Synth. Met., 56, 3305 (1993); D. Shiomi, K. Ito, M. Nishizawa, A. Hase, K. Sato, T. Takui, and K. Itoh, Mol. Cryst. Liq. Cryst., 334, 99 (1999); D. Shiomi, M. Tamura, H. Sawa, R. Kato, and M. Kinoshita, j. Phys. Soc. Jpn., 62, 289 (1993).
32. L. Catala, J. Le Moigne, N. Kyritsakas, P. Ray, J. J. Novoa, and P. Turek, Chem. - Eur. J., 7, 2466 (2001); H. Oshio, A. Ohto, J. Fujisawa, T. Watanabe, T. Ito, and K. Isobe, Chem. Lett., 1994, 2353; T. Sugano, M. Tamura, and M. Kinoshita, Synth. Met., 56, 3305 (1993); D. Shiomi, K. Ito, M. Nishizawa, A. Hase, K. Sato, T. Takui, and K. Itoh, Mol. Cryst. Liq. Cryst., 334, 99 (1999); D. Shiomi, M. Tamura, H. Sawa, R. Kato, and M. Kinoshita, j. Phys. Soc. Jpn., 62, 289 (1993).
33. L. Catala, J. Le Moigne, N. Kyritsakas, P. Ray, J. J. Novoa, and P. Turek, Chem. - Eur. J., 7, 2466 (2001); H. Oshio, A. Ohto, J. Fujisawa, T. Watanabe, T. Ito, and K. Isobe, Chem. Lett., 1994, 2353; T. Sugano, M. Tamura, and M. Kinoshita, Synth. Met., 56, 3305 (1993); D. Shiomi, K. Ito, M. Nishizawa, A. Hase, K. Sato, T. Takui, and K. Itoh, Mol. Cryst. Liq. Cryst., 334, 99 (1999); D. Shiomi, M. Tamura, H. Sawa, R. Kato, and M. Kinoshita, j. Phys. Soc. Jpn., 62, 289 (1993).